Study On The Removal Of Phosphate And Estrogens In Reclaimed Water Using Lanthanum Modified Pine Needles And Magnetic Graphene Oxide

Pine needles gathered from the woods of Northeast Normal University was used as raw material for generating Lanthanum modified pine needles(LH pine needles) by alkali-isopropanol treatment and chemical precipitation. The magnetic graphene oxide(MGO) was successfully synthesised by the in situ chemical co-precipitation method with Fe3+, Fe2+and graphene oxide(GO) in laboratory. The removal characteristics and mechanism of phosphorus and estrogens by LH pine needles and MGO in reclaimed water was systematically studied by using shake flask experiments and column experiments, respectively. Results shows that the LH pine needles was effective on the removal of phosphorus while the MGO could effectively adsorb estrogens at μg/L level.The renewable pine needles was used as an adsorbent to remove phosphorus from aqueous solutions. Using batch experiments, pine needles pretreated with alkali-isopropanol failed to effectively remove phosphorus, while pine needles modified with lanthanum hydroxide(LH) showed relatively high removal efficiency.LH pine needles were effective at a wide pH ranges, with the highest removal efficiency reaching approximately 97% at a pH of 3. The removal efficiency was kept above 69% using 10 mg/L phosphorus solutions at desired pH values. There was no apparent significant competitive behavior between co-existing anions of SO42-, NO3-,and Cl-. however, CO32-exhibited increased interfering behavior as concentrations increased. An intraparticle diffusion model showed that the adsorption process occurred in three phases, suggesting that a boundary layer adsorption phenomena slightly affected the adsorption process, and that intraparticle diffusion was dominant.The adsorption process was thermodynamically unfavorable and non-spontaneous;temperature increases improved phosphorus removal. Total organic carbon(TOC)assays indicated that chemical modification reduced the release of soluble organic compounds from 135.6 mg/L to 7.76 mg/L. This new information about adsorption performances provides valuable information, and can inform future technological applications designed to remove phosphorus from aqueous solutions.Adsorption equilibrium of 200 μg/L of estrogens on MGO could be achieved within 15 min, with more than 80% of the removal efficiency was obtained, among which, the removal efficiency of E1 and EE2 reached over 90% of adsorptionefficiency. Adsorption of estrogens on MGO fitted Pseudo-second-order kinetics. The stronger the hydrophobicity of estrogens is, the easier estrogens could be adsorbed on MGO. Adsorption process of four types of estrogens on MGO was endothermic,except for E3 as exothermic process. Increasing of temperature could increase the adsorption process of four types of estrogens while the effect of temperature on adsorption of E3 was hard to be accounted. However, pH had significant effect on adsorption of E3 on E3. In specific, the adsorption efficiency declined from 88.6% to7.3% when pH increased from 3 to 11. On the contrary, pH had little effect on adsorption of other four estrogens on MGO. Ion exchange, electrostatic interactions and π-π dispersion effect played main role in estrogens adsorption process on MGO.Column filled fixed bed experiments was simulated to remove phosphorus and estrogens in water body. Phosphorus adsorption efficiency on LH pine needles in column experiments was significantly lower than that in flask shaking experiments and the apparent estrogens adsorption on MGO in column experiments was lower than results in flask shaking experiments. Combined media of LH pine needles and MGO achieved in promising filtration and interception effect and furthermore, LH pine needles and MGO had synergic cleaning effect, of which mechanism was in need of further analysis. Along with the rising of pH, combined media achieved higher efficiency on removal of phosphorus and estrogens. However, the removal margin was not apparent in neutral and alkaline condition. Penetration volume of phosphorus and estrogens declined significantly along with the increase of flow velocity.Combined media filtration bed could result in 87% of estrogens removal at μg/L level in secondary effluent from municipal sewage plant, which showed positive practical application potential to control trace estrogens in water body.